A Basic Text-Based Recording Studio

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Overdubbing of Subsequent Tracks

Unless you're recording a live stereo track, you're likely to want to
overdub other tracks. It is possible to use Ecasound to listen to tracks
you've already recorded while recording (and listening to) a new track.

To listen to an already-recorded track while recording a second track,
create three Ecasound chains (Table 2).

Table 2. Chains for Listening to an Already-Recorded Track While
Recording a Second Track

Chain

Input Source

Output Destination

1

track1.wav

JACK

2

JACK

JACK

3

JACK

track2.wav

Creating a chain setup like this causes the contents of track1.wav to
be sent to JACK to be played, and any input from JACK is sent back
to JACK and saved to a file called track2.wav. track2.wav
will contain only the new track—not the new track mixed with the old
track. We'll mix them later.

Converting this chain setup to an actual Ecasound command is
straightforward:

Recording further tracks is a similar process. We create a chain
for each of our already-recorded tracks and set their output to JACK. We
also set up two chains to take input from JACK and send it to a file and
back to JACK, so we can hear it. The chain setup in Table 3 would
suffice.

I'm not a drummer, but some of the things I record need drums. Although
the Hydrogen drum machine is probably the best that I have seen on Linux,
it hasn't yet attained the magical 1.0 version number and isn't yet
perfect. One feature that's broken in the snapshot I'm running is the ability
to export to a PCM audio .wav file. As luck, or rather good design,
would have it, Hydrogen can use JACK to output digital audio.

To use JACK and Ecasound to record the output of an audio application
such as Hydrogen, we can perform the following steps:

Configure Hydrogen to use JACK for its output.

Configure Hydrogen to play in song mode, as opposed to pattern mode.

Execute the the following command:

ecasound -a:1 -i jack_auto -o drum_track.wav -G jack,ecasound,recv

Click the play button in Hydrogen.

The above command configures a single chain within Ecasound that draws
input from JACK and sends output to a file called drum_track.wav. The
-G jack,ecasound,recv instructs Ecasound to listen to JACK for a start
command, which is sent when we click the Play button in Hydrogen,
as a JACK client called ecasound.

It can take a second or so for Ecasound to start and initialise after
receiving the start command, so I like to have a pattern of silence at
the start of the Hydrogen track.

Unless you have impeccable timing, you would most likely record any
software sources first. It is harder to synchronise a software source,
such as a drum machine, with an existing human-recorded track than is is
to record the human tracks around the machine-created tracks. This
includes any MIDI tracks you intend to use.

Mixing All Tracks to a Single Stereo Master

At this point, we have a series of .wav files that correspond to each
of the audio tracks we have recorded. Should we need to, we could use
Ecasound, SoX or even Audacity to add effects or make minor corrections
or alterations to any of the tracks. Once we're happy with the individual
tracks, we can mix a single master track.

The process of turning our multiple tracks into a single stereo master
track is straightforward. We create a chain for each track and
set the output to be a .wav file.

Table 4. Turning Multiple Tracks into a Single Stereo Master

Chain

Input Source

Output Destination

1

track1.wav

all_tracks.wav

2

track2.wav

all_tracks.wav

3

track3.wav

all_tracks.wav

Ecasound provides a means to make this particular case easier. The all
pseudo-chain name can be used to redirect the output of all of our tracks
to a single place, namely a file called all_tracks.wav:

You also can attach a series of effects, including reverb,
compression and amplification to each chain before it is written to
the output destination. It is even possible to add delay and alter the
panning of a particular track or even perform noise reduction;
however, such topics are beyond the scope of this article.

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